Known antenna elements of this type are made by means of boards (often printed boards), each including two orthogonal feedlines which are generally coplanar and which are associated with one or two flat obstacles of the "patch" type comprising an "active" patch coupled to the two feedlines and optionally a "passive" other patch overlying the first patch and performing the function of spreading the passband.
Such known structures suffer from the major drawback of not allowing satisfactory decoupling to be achieved between the two orthogonal polarizations over a wide passband, thereby making it possible to achieve the characteristics of purity that are often currently desired.
In attempts to improve the performance levels of arrays of antennas of this type, the following has already been proposed:
separating the arrays of radiating elements electrically and physically so as to obtain one array for each of the two crossed polarizations;
geometrically interlacing the two resulting single-polarization radiating arrays to form one array; and
grouping the radiating elements operating in dual-polarization mode together into well-defined sub-arrays fed via phase-shifters so as to cancel the cross-polarization radiation on the axis of the antenna.
However, all those ways of solving the problems do not make it possible to obtain arrays that are sufficiently compact and lightweight to be compatible with certain requirements, especially in the case of antennas on-board satellites. Moreover, as yet, the quality of polarization separation remains insufficient when a wide passband is desired.